Field of Invention
Various embodiments of the present disclosure relate to a laser beam combination system.
Description of Related Art
A plurality of laser beams may be combined to increase power when power of one laser beam, which is in use, is insufficient. Examples of a method of combining the plurality of laser beams may include coherent beam combining, spectral beam combining, and geometrical beam combining methods.
When the plurality of laser beams are combined using the geometrical method, phases or wavelengths of the laser beams may not be adjusted. Accordingly, costs are low, and power of the beam may be increased using a relatively easy method. Particularly, the geometrical method may be representatively used when laser diode beams for pumps used in an optical fiber laser are combined.
The laser diode is a semiconductor light source, and is frequently used as a pumping light source for a solid state laser or an optical fiber laser.
FIG. 1 is a view showing a type of beam radiated from a laser diode bar.
As shown in FIG. 1, the beam is radiated from the laser diode at a large radiation angle 112 in a y-axis direction, which is perpendicular to an arrangement direction of radiators 100, that is, a fast axis direction, and at a small radiation angle 114 in an x-axis direction, which is parallel to the arrangement direction of the radiators 100, that is, a slow axis direction.
A cylindrical lens having a high numerical aperture (hereinafter, ‘NA’) should be used in order to collimate the fast axis beams having the large radiation angle. The quality of the beam is improved as the width 122 of the single radiator is reduced, and heat is easily emitted as the interval 124 between the radiators is increased. That is, there are spaces, through which light is not emitted, between the radiators, and the spaces may act as a factor reducing the quality of the beam. Further, when the laser diode is combined with the optical fiber, the quality of the beam may be reduced due to asymmetry between the fast axis and the slow axis.
FIGS. 2A and 2B are views showing beam patterns at ends of optical fibers. When a long rectangular beam 210 of the single radiator is received using the optical fiber, large empty spaces are formed in a fast axis direction as in FIG. 2A. In order to solve the aforementioned problem, a technology using a stair-type heat sink has been proposed.
Specifically, laser diodes may be disposed so that beams are stacked to increase the total height of the beams in a fast axis direction, and accordingly, the beams emitted from the laser diodes may be combined to form a square shown in FIG. 2B, thereby increasing the light filling efficiency of the optical fibers. However, the technology has a drawback in that since very precise processing is required when the stair-type heat sink is manufactured, it is difficult to perform the manufacturing process.